1. Field of the Invention
The present invention relates to a case unit with an opening covered with a light transmission member, a portable apparatus including such a case unit, and a method for assembling such a case unit.
2. Description of the Related Art
As a case unit with an opening covered with a light transmission member, there are known, for example, a case unit for a time piece including a wristwatch, a case unit for a cellular phone, a case unit for a PDA (Personal data assistance), a case unit for a portable audio player, a case unit for a portable or small-size radio and the like.
For example, a conventional case unit for a wristwatch is described in Japanese Patent Application KOKAI Publication No. 2000-329869.
The conventional, case unit for a wristwatch comprises a metal case having a watch module storage space which stores a watch module with a plurality of watch hands for indicating a time, and a watch glass as a light transmission member which covers an entrance opening of the watch module storage space of the metal case and through which the watch hands of the watch module can be seen from an outside of the metal case. The watch glass is fitted in the entrance opening with a watch glass fixing and waterproofing packing between an outer peripheral surface of the watch glass and an inner peripheral surface of the entrance opening of the watch module storage space. Further, an outer peripheral area on an external surface of the watch glass is covered with an annular bezel which is placed at an entrance opening peripheral area that encloses the entrance opening of the watch module storage space on an external surface of the metal case, and the annular bezel is fixed to the entrance opening peripheral area on the external surface of the metal case by fixing screws.
The metal case is relatively heavy, and a process thereof is complicated and comparatively expensive. Furthermore, the fixing screws that are used for fixing the watch glass together with the watch glass fixing and waterproofing packing to the entrance opening of the watch module storage space of the metal case complicates a watch glass fixing structure of the conventional case unit for a wristwatch and further complicates an assembling of the conventional case unit for a wristwatch.
There was a proposal in which the annular bezel is fixed to the entrance opening peripheral area on the external surface of the metal case by using a double-coated adhesive tape instead of the fixing screws. However, after a long time use or in an exposure test to a high temperature for a long time, a performance of the double-coated adhesive tape was deteriorated.
A wristwatch using a synthetic resin case instead of the metal case is conventionally used. Since an elasticity of the synthetic resin case is higher than that of the metal case, in order to prevent the watch glass together with the watch glass fixing and waterproofing packing from being easily fallen from the entrance opening of the watch module storage space of the synthetic resin case when the synthetic resin case receives an impact from its outside, after it is used for a long time period, or in an exposure test to a high temperature for a long time, a watch glass fixing structure such as, for example, the annular bezel using the fixing screws as described above, which has a physically high durability but has a complicated structure whose assembly is cumbersome, must be employed.
The present invention has been derived from the above described circumstances, and an object of the present invention is to provide a case unit with an opening covered with a light transmission member, which has an simple structure, which is easy to be assembled and, even if a synthetic resin case, which is inexpensive and whose production cost is inexpensive, is used instead of a metal case, which can prevent a light transmission member from being easily fallen from the synthetic resin case after a long time period or in an exposing test to a high temperature for a long time. And another object of the present invention is to provide a portable apparatus including such a case unit with an opening covered with a light transmission member, and a method for assembling such a case unit with an opening covered with a light transmission member.